Apparatus for detecting phosphorus and/or sulphur in gases



1966 c. E. VAN DER SMISSEN 3,

APPARATUS FOR DETECTING PHOSPHORUS AND/OR SULPHUR IN GASES OriginalFiled Jan. 10, 1962 INVENTOR Carl Ernst van o'er Smz'ssefl BY &

M d M g ATTORNEYS United States Patent 4 Claims. 61. 23-253 This is adivision of my application S.N. 165,543, filed Jan. 10, 1962,forfProcess for Detecting Phosphorus and/ or Sulphur in a Gas, nowPatent No. 3,213,747.

This invention relates to the detection of the presence of phosphorusand/or sulphur containingcompounds in air or other gases.

In particular, this invention is directed to the process for thequantitative determination of phosphorus or sulphur containing compoundsby means of the coloration of a hydrogen flame. In this invention, thegas to be analyzed either contains oxygen or oxygen is added thereto,and then the gas is mixed wit-h hydrogen, with the amount of hydrogenbeing in excess of that required for the complete reaction of the oxygencontained in the gas. Finally, the mixture of gas with oxygen is ignitedto obtain a color produced by the resulting flame. The invention has theadvantage of giving a great sensitivity of detection.

In a modified form of the invention, it the gas to be analyzed does notcontain oxygen, a separate oxygen stream is introduced into the hydrogenstream along with the gas to be analyzed. In this mixture, the quantityof hydrogen is again greater than that needed for the complete reactionof the oxygen. This modification is also of great sensitivity fordetecting the presence of phosphorus or sulphur in the gas.

The means by which the objects of the invention are obtained aredescribed more fully with reference to the accompanying schematicdrawing of the apparatus used.

The burner is composed of two parts. The first part is a quartz tube 1having inlet 2 for the gas to be tested and a conical portion 3 drawnout into a fine bore tube 4, the upper end of which is open. Tube 4 ispartially telescoped within a quartz, Pyrex or high temperatureresistant glass tube or cylinder 5, the lower end 6 of which is seatedon the conical portion 3. Hydrogen is introduced adjacent the lower endof tube through inlet pipe 7. Tube 5 is cooled by a cooling agent suchas water entering pipe 8 into water jacket 9 which surrounds tube 5, thecooling agent being exhausted through pipe 10. The upper end 11 of tube5 is an external burner tube for the formation of an upper flame, whilea lower first flame 12 is formed at the outlet end of tube 4 and thisflame produces a glow zone 13.

In operation, the gas such as air containing either phosphorus orsulphur compounds flows through into inlet 2 of pipe 1 and through tube4. At the same time, hydrogen enters through pipe 7. The velocity of theair in pipe 1 is about from 0.3 to 0.6 liter per minute and the velocityof the hydrogen is from about 0.1 to 0.4 liter per minute. The hydrogenis ignited at the upper end 11, and the flame strikes back to ignite thefirst lower flame 12. Tube 5 is cooled by the water jacket 9 and intensecooling causes the water formed by the flame 12 to collect on the innerwall of tube 5, which water drops to the drain pipe 16 closed by thestopcock 17. When the gas being tested is free from sulphur andphosphorus compounds, the flame 12 is bluish-white. This flame 12 hasabout the diameter of tube 4 and a length of from about 3 to 5 mm. Ithas a type of semi-circular to elliptical shape. The

3,290,118 Patented Dec. 6 1966 upper flame has an inner coloration 14and an outer conical shape 15. In the absence of phosphorus or sulphur,it has only a slight bluish, reddish, or yellowish glow depending uponthe color of the glass tube 5.

When the gas being tested contains phosphorus compounds, the flame 12has an intensified whitish coloration and the edge of flame 15 iscolored somewhat whitish to yellowish. In the glowing zone 13 aboveflame 12, a green color appears at a'distance. of from about one to twotimes the length of flame 12 above the top of flame 12 and which has adecreased intensity in an upward direction. This green colorationappears a second time at the end 11 of tube 5 in the form of a verysharply defined cone 14 withinflame 15.

When the gas being tested contains a sulphur compound, no change occursin the coloration of flames 12 and 15. However, a. bluish colorationappears inthe glow zone 13 instead of the greenish phosphorus color.This bluish color appears somewhat higher above the tip of flame 12 thanthe greeen phosphorus color. Again, cone 14 in flame '15 has a bluesulphur color instead of the green phosphorus color.

When both phosphorus and sulphur compounds are found in the gas beingtested, a blue color appears above a green color in the glow zone 13.The cone 14 is colored either blue or green according to thepreponderance of either sulphur or phosphorus compounds in the gas.

The colors were determined in zone 13 with the aid of aspectrophotometer 18. The green phosphorus color was measured on the 520millimicron line, and the blue sulphur color was measured on the 380millimicron line. The colors in cone 14 can be determined in a likemanner. According to the concentration of either phosphorus or sulphurin an amount of about 10- grams per liter of air, the characteristicglow of both flames 12 and 13 is substantially unaffected by slightchanges in the intensity of flame 12. Therefore, both colored zones 13and 14 are well suited for measuring purposes. When the concentrationdrops to about 10 grams per liter of air, the intensity of the color isdetermined by the first or lower flame 12. This concentration is verysensitive to the fluctuations of the quantities of air and hydrogen sothat it is not constant with a change in the intensity of flame 12 atthe maximum sensitivity obtainable. Therefore, only the glowing zone 13between flames 12 and 15 is usable. The optical axis of thespectrophotometer was set to transverse tube 5 about from five tofifteen times the length of flame 12 above flame 12 for measuring theblue sulphur coloration. When measuring the green phosphorus color, theaxis was positioned from about one to two times the length of flame 12above flame 12.

The size of the burners can be selected to give the velocity of the gasand hydrogen flows as required. The water jacket 9 can be replaced byair cooling, and also the flame temperatures can be lowered by dilutingthe combustion gases with nitrogen or other inert gas. By setting thespectrophotometer upon the corresponding two wave lengths, namely 520and 380 millimicrons, the combined presence of both phosphorus andsulphur can be determined. Also, the determination can be carried out atother wave lengths since the spectral bands employed are wide and thegiven wave lengths of 520 and 380 millimicrons designate only thesharpest lines. The detection of phosphorus or sulphur in air is shownby the following example.

The air to he tested and suspected of containing a phosphorus compound,such as tricresyl phosphate, phosphorus oxychloride and sulphurcompounds such as sulphur dioxide, di-methyl sulfoxide or thiophene, wasintroduced through tube 1 and the hydrogen was introduced throwgh tube7. The gas mixture was ignited in the burner tip 11. Thereupon, theflame struck back 3 and ignited the lower or first flame 12 inside tube5. The water cooling was turned on and the spectrophotometer 18 set tothe readings on the wave lengths -20 and 3 80 millimierons. The opticalaxis of the photometer was set to be selectively centered at either fromabout one or two times or from five to fifteen times the length of flame12 above flame 12.

When only a few micrograms of phosphorus or sulphur containing compoundswere in a cubic meter of air, the photometer showed the presence of adistinct color in the glow zone 13, this color being green forphosphorus and blue for sulphur. The observation of a specific color wasfacilitated by using a light filter 19 which filtered only pure greenlight for the phosphorus observation and a pure blue light for thesulphur observation.

Having now described the means by which the objects of the invention areobtained, I claim:

1. An apparatus for detecting the presence of phosphorus or sulphurcompounds in a gas comprising a high temperature-resistant transparentcylinder for containing gas, a fine bore glass burner tube partiallyteleseoped within said cylinder through an opening in said cylindersealed against the entry of air, means for introducing the gas into saidburner tube and directly into said cylinder, and means for introducinghydrogen directly into said cylinder as a fuel for mixing with said gasand forming a glow zone in said cylinder from the flame producedthereby.

2. An apparatus as in claim 1, further comprising a cooling jacketsurrounding said cylinder.

3. An apparatus as in claim 2, further comprising a spectrophotometermounted adjacent said cylinder for determining the presence ofphosphorous in the range of about 5 20 millimicrons, and the presence ofsulphur in the range of about 380 rnillimicrons.

4. An apparatus as in claim 2, further comprising a light filter mountedbetween a photometer and said gas cylinder for transmitting light onlyin the range of about 520 milllirnicrons when detecting (forphosphorous, and of about 380 millirnicrons when detecting for sulphur.

References Cited by the Examiner UNITED STATES PATENTS 2,200,523 5/1940Tuel 23254 2,589,116 3/ 1952 Nolcken 23154 2,76 0,005 1,/ 6 Vonnegut23154 2,779,666 1/1957 Ant-hes 23254 2,809,101 10/1957 Mitchell 23254OTHER REFERENCES Wickbold, Angewandet Chemie, Jahrg. 69, pp. 530- 533,1957.

MORRIS o. WOLK, Primary Examiner.

Z. PAROCZAY, Assistant Examiner.

1. AN APPARATUS FOR DETECTING THE PRESENCE OF PHOPHORUS OR SULPHURCOMPOUNDS IN A GAS COMPRISING A HIGH TEMPERATURE-RESISTANT TRANSPARENTCYLINDER FOR CONTAINING GAS, A FINE BORE GLASS BURNER TUB PARTIALLYTELESCOPED WITHIN SAID CYLINDER THROUGH AN OPENINNG IN SAID CYLINDERSEALED AGAINST THE ENTRY OF AIR, MEANS FOR INTRODUCING THE GAS INTO SAIDBURNER TUBE AND DIRECTLY INTO SAID CYLINDER; AND MEANS FOR INTRODUCINGHYDROGEN DIRECTLY INTO SAID CYLINDER AS A FUEL FOR MIXING WITH SAID GASAND FORMING A GLOW ZONE IN SAID CYLINDER FROM THE FLAME PRODUCEDTHEREBY.